1. Field of the Invention
The present invention relates generally to passive optical devices used in optical telecommunication systems, and particularly to optical splitters modules.
2. Technical Background
One of the current trends in telecommunications is the use of optical fibers in place of the more conventional transmission media. One advantage of optical fibers is their larger available bandwidth handling ability that provides the capability to convey larger quantities of information for a substantial number of subscribers via a media of considerably smaller size. Further, because lightwaves are shorter than microwaves, for example, a considerable reduction in component size is possible. As a result, a reduction in material, manufacturing, and packaging costs is achieved. Moreover, optical fibers do not emit electromagnetic or radio frequency radiation of any consequence and, hence, have negligible impact on the surrounding environment. As an additional advantage, optical fibers are much less sensitive to extraneous radio frequency emissions from surrounding devices and systems.
With the advent of optical fiber networks, flexible switching devices are needed to direct light signals between fibers in an all-optical domain fiber network. An optical splitter is a type of optical switching device that takes an incoming optical signal and splits it between two or more outputs. The number of splits depends on the particular application. Because the signal is split into two or more signals, the splitter is also an attenuator whose attenuation is proportional to the number of splits. Optical splitters, also referred to as “splitter modules” because of their modular construction, have a number of shortcomings that, if improved upon, would result in a more robust splitter module for certain applications.
One splitter module shortcoming involves the need to use external attenuators for certain applications. For FTTx systems with link budgets designed for a particular number of splits, a reduced number of splits may be required, but with the same attenuation. For example, for a splitter module having a splitter chip designed for 1×32 splits (15-17 dB IL), a 1×4 splitter chip may be needed, where each of the 4 splitter output ports serves electronics that connect eight customers in a multi-dwelling unit (MDU) (the 1×4 optical split still serves thirty-two customers). The optical power required by the receiving electronics, however, may still be in the 15-17 dB range, while the 1×4 splitter module delivers 6-8 dB. of optical power. This necessitates attenuation of the splitter output from 6-8 dB to 15-17 dB. This is typically accomplished using an attenuator external to the splitter. However, this adds complexity and expense to the splitter system and also makes it less compact.
Another shortcoming is that present-day splitter modules consist of separate parts: a standard splitter unit (that includes a fiber array, a splitter chip, and a ferrule) and external connectors that attach thereto. External connectors are connected to the module to establish communication through the module between remote devices. Considerable simplification and cost reduction for splitter modules could be realized if an external multi-fiber connector could be directly connected to the planar splitter chip rather than using separate connectors. Likewise, considerable simplification and cost reduction (and cost predictability) for splitter modules could be realized if a compact splitter module could be constructed that serves as both as device and module without the usual distinction between the two.